Method of manufacturing, by photographic agency, internal and/or external images on and/or in macromolecular supports with mercury and silver salts germ introduction baths



Apnl 21, 1964 c. J. DIPPEL ETAL 3,130,052

METHOD OF MANUFACTURING, BY PHOTOGRAPHIC AGENCY, INTERNAL AND/0R EXTERNAL IMAGES 0N AND/OR IN MACRO-MOLECULAR SUPPORTS WITH MERCURY AND SILVER SALTS GERM INTRODUCTION BATHS 2 Sheets- Sheet 1 Filed July 11, 1960 A MR Em qozw 2 0 T n .1 m I :llll llll llillllllli 2 g I ML H MMW WWW MMWWW HH W n 22 5 n. -imullmnimuw law E5: ww wqo zv L E0? 0nd e; 3 1||I||l:|||! |1ll V u ilk llllln 2 9 n I l l l i ll 8 on 1 3 w ll-II lllilllllll lllllllll 11 3658i b? d I EEEI--- 8N NQR BY ll-hut 1e AGEN April 1964 c. J. DIPPEL ETAL 2 METHOD OF MANUFACTURING, BY PHQTOGRAPHIC AGENCY, INTERNAL AND/OR EXTERNAL IMAGES ON AND/OR IN MACRO-MOLECULAR SUPPORTS WITH MERCURY AND SILVER SALTS GERM INTRODUCTION BATHS Filed July 11, 1960 2 Sheets-Sheet 2 BY v V w m AGE United States Patent sassnsz ivmruon or MANUFATUREJG, er Prroro- It is known to manufacture, by photographic agency, internal and/or electrically conductive external noblemetal images in and/ or on non-metallic supports by purely physical development of mercury germs, obtained by converting a light-sensitive compound in a support by exposure into one or more other compounds, hereinafter termed the light-reaction product, which is caused to react, in the presence of moisture, with mercurous ions. In this mercurous system a mercurous salt may be caused to react either in the layer containing the lightsensitive compound prior to exposure or a solution of mercurous salt may be caused to react with the exposed layer. In the first-mentioned variant the preservability of the light-sensitive layer is, as a rule, very restricted; moreover, the results are, in general, insufiiciently reproducible. In view of the poisonousness of mercury vapour there are, moreover, hygienic drawbacks and, in addition, by using this variant, no external metal germ images can be obtained. For this reason the second variant (the so-called germ introduction method) would be preferable. However, hitherto it could not be employed generally, since, for example, when using ortho-hydroxy-benzenediazoniumor ortho hydroxy naphthalene diazoniumcompounds as light-sensitive substances, the images then obtained exhibited a light-sensitivity and density which are insufficient for most uses. On the contrary, the germ introduction method, when using aromatic diazo-sulphonates as light-sensitive compounds, preferably in conjunction with so-cailed anti-regression agents (i.e., substances preventing the diazo-sulphonate from being regenerated from its light-reaction product, a known antiregression agent is, for example, cadmium lactate) yields satisfactory results. But even in the latter case the mercurous system is characterized by a comparatively low light-sensitivity, so that it is, for example, less suitable for manufacturing magnifications.

The mechanism of the present image formation is based of the fact that the aforesaid light-reaction product is capable of producing, in the presence of moisture, a so-called disproportioning of mercurous salts. This disproportioning is performed in accordance with the reaction equation:

The mercury atoms thus set free unite to form mercury drops, which together, form the mercury germ image. Otherwise it is immaterial for the result of the image formation whether the mercury is obtained only by disproportioning or partly by reduction.

The term purely physical development, referred to above, is to be understood to mean the intensification of a weak photographic metal germ image into an image of the desired optical density or with the required quantity of image metal, Whilst, from the beginning, a watersoluble, reducible metal compound is provided and the image metal obtained by reduction With the aid of a photographic reducing agent originates, at least for the major part, from the metal ions or complex metal ions provided by the aforesaid metal compound.

ice

In purely physical developers, in conjunction with photographic reducing agents, only ions and complex ions of metals nobler than copper, for example, silver, gold, platinum, and so on, can be employed. A frequently used physical developer is, for example, a solution of silver nitrate in water, to which is added hydroquinone, metol or p-phenylene-diamine. Such a developer contains furthermore, as a rule, in order to improve its preservab'dity or to control the speed of development, further substances, for example, organic acids, buffer mixtures or substances reacting with the noble metal compound whilst forming complex compounds. In this purely physical development the mercury drops forming the mercury germ image operate as germs, on which free noble metal formed from the noble-metal salt by reduction is deposited. In general, this involves a material intensification of the image, since the quantity of noble metal deposited on the mercury germs is, as a rule, many times larger than the quantity of mercury of the mercury germs together.

However, a purely physical developer, even if it is not used, deteriorates rapidly, whilst separating out noble metal. This spontaneous decomposition may be considerably delayed, so that the developer may be used for a considerably longer time, by adding one or more suitable ionogenic surface-active compounds, in conjunction or not in conjunction with a non-ionogenic, surface-active compound to the developer. A physical development, in which this stabilizing eifect is realized, is termed a stabilized, physical development. On the contrary, a physical development in which this stabilizing effect is not used, is termed a non-stabilized physical development.

With the aid of the variant set forth of the mercurous system, in which germ introduction is used, internal, photographic noble-metal images, lying below or in the surface of the support, and external electrically conductive, photographic noble-metal deposits on or at the support surface can be manufactured.

The latter images may be distinguished by so-called grown external metal images, which are obtained by development with the aid of a non-stabilized physical developer, of an at least partly external metal germ image, which is produced in itself by employing special exposure energies, i.e., the so-called mirror exposures, and the so-called outgrown external noble-metal images, obtained by developing for such a long time the internal part of the metal germ image obtained by using a so-called outgrowth exposure, with the aid of a stabilized, if necessary activated, purely physical developer, which may be refreshed or regenerated, that this metal germ image grows out into an external noble-metal layer. The lastmentioned class of external images exhibits, as a rule, a materially improved adhesion to the support as compared with the first-mentioned images.

The term mirror exposure is to be understood to mean that exposure energy per surface unit of the lightsensitive layer which, with the chosen concentration of metal ions in the germ introduction bath, provides an at least partly external metal germ image, which after intensification by means of the selected, non stabilized, purely physical developer, under chosen conditions of temperature and developing time, yields an external noble-metal layer which, subsequent to washing in water and to heating at 150 C. for one hour, has an electric resistance not exceeding ohms per square surface.

The term of outgrowth exposure is to be understood to mean herein that exposure energy per surface unit of the light-sensitive layer which, with the chosen concentration of metal ions in the germ introduction bath, provides a metal germ image which, subsequent to intensification by means of a stabilized, purely physical developer obtained by dissolving, in distilled water,

Metol (0.025 mol/litre),

Citric acid (0.10 mol/litre),

Silver nitrate (0.01 mol/ litre), Lissapol N (0.02% by weight), Armac 12 D (0.02% by weight),

at a temperature of 20 0., within 180 min, the developer being refreshed after 60 min. and 120 min, yields an external noble-metal layer, which, after having been washed in water and then heated at 150 C. for one hour, exhibits an electric resistance not exceeding 100 ohms per square surface. Owing to this thermal after treatment it can be assessed in a satisfactorily reproducible manner whether a given exposure is a mirror exposure or an outgrowth exposure or not. It may occur, however, that a given support material cannot withstand such a thermal treatment. In this case a less reproducible measurement on a layer not after-treated in this manner must be taken for granted; in the case of a mirror exposure or an outgrowth exposure the electric resistance must not exceed ohms per square surface.

For the manufacture of internal, photographic noblemetal layers use will therefore be made, preferably, of exposure energies which are weaker than a mirror exposure. The growth of a metal germ image, which may still be partly external but which is insufiicient to form a grown external image with reproducible properties, may then be prevented by using stabilizers in the physical developer with the aid of which the limit of the mirror exposure has been assessed. In this case the developing time must not be prolonged to an extent such that the development image grows out of the support.

The light-sensitivity of the described variants of the mercurous system can be increased by enhancing the number of developable mercury germs. Such an increase may be achieved by providing in the layer, prior to the pure physical development, a compound which contains an anion which is capable of reducing the concentration of the free mercurous ions, and which does not form a permanent precipitate with the mercurous ions under the prevailing conditions. Anions of the said kind are, for example, the lactate ion, the citrate ion and the acetate ron.

By using coloring, purely physical developers coloured images can be obtained with the aid of the aforesaid metal images, the metal images concerned may, if desired, be removed afterwards, so that only the colour images are left. mainly in the field of the normal, internal photographic images.

The invention has for its object to enhance the lightsensitivity of the photographic material processed by the germ introduction method of the mercurous system by a further increase in the number of developable germs, whilst it is at the same time intended to act upon the characteristic curve of this material. It is based on the known method in which a support containing at least one light-sensitive compound of which the light-reaction product is capable of producing metallic mercury from mercurous ions in the presence of moisture, is exposed and then treated with a Water-containing solution of one or .more mercurous salts (which solution will be termed herein the germ introduction bath), followed by stabilized or non-stabilized purely physical development of the mercury germ image thus formed. In accordance with the invention it has now been found that the number of developable germs and hence the light-sensitivity in these known methods for the manufacture of photographic in- The use of the coloring physical development lies U characteristic curve of the processed photographic material increases, as a rule, which may frequently be observed already before a gain in absolute sensitivity of the material can be assessed. Conditions are apparently such that the increase in the number of germs is stronger according as the concentration of the light-reaction product and hence the exposure energy employed are higher.

In principle, all light-sensitive compounds of which the light-reaction product is capable of producing metallic mercury from mercurous ions in the presence of moisture can be employed in the method according to the invention. A relative, very considerable improvement in the light-sensitivity and the density (gradation) occurs, when using the aforesaid hydroxy-benzene-diazonium compounds and hydroxy-naphthalcne-diazonium compounds, which, as stated above, were hitherto substantially unemployable for the use of the germ introduction method of the mercurous system. Nevertheless, in absolute sense, the highest sensitivities are achieved when using the aforesaid diazo-sulphonates as light-sensitive compounds, preferably in conjunction with the above-mentioned antiregression means.

For the sake of efiiciency the total concentration of the mercurous salts in the germ introduction bath is chosen to be not lower than 1 mol/ litre and preferably between 0.5 and 10 mmol/litre.

As far as the concentration of the silver salts in the germ introduction bath is concerned, the following should be noted. It has been found that, when a given total concentration of the silver salts in the germ introduction bath, which concentration will be termed herein the activating concentration, is exceeded, a gain in sensitivity and/ or an increase in the steepness of the characteristic curve are introduced. At a further increase in the concentnation of the silver salt the sensitivity and the steepness increase further until a maximum is attained, after which these effects diminish, often even to an extent such that they vanish completely and even become negative. The maximum of the sensitivity and of the steepness do not appear to occur always with the same silver salt concentration. The total concentration of the silver salts at which the two effects are lost will be termed herein the de-activating concentration.

The technical effects aimed at herein are influenced by many factors. For example, both the activating concentration and the de-activating concentration, referred to above, vary in accordance with the concentration of the mercurous salt, the nature of the support layer, the acidity of the germ introduction bath, the kind of lightsensitive compound, the manner of purely physical development, the absence or presence of an anti-regression agent and, in the latter case, the nature thereof. If internal photographic noble-metal images, hereinafter to be referred to as 1B. are to be manufactured, both the increase in sensitivity and the gradation control may be utilized to advantage. With the formation of external, electrically conductive, photographic noblemetal deposits, hereinafter referred -to by. the abbreviation U.B., distinguished in grown external images A.U.B. and outgrown external images U.U.B., a socalled all-or-nothing reproduction is concerned; in this case the increase in sensitivity is of direct importance. In connection herewith and with a view to the dependence of the activating and de-activating concentrations upon all kinds of factors, referred to above, various criteria are applied to the determination of these activating and de-activating concentrations, which criteria rnatch the nature of theuses in the fields of LB, A.U.B. and U.U.B. The regions of active concentrations determined in accordance with these criteria will, as a rule, not cover each other completely.

If I.B.-uses are aimed at, to which end the method according to the invention is to be employed to control 7 ments of the steepness of the density characteristic curve. However, if a sensitivity effect is to be obtained, this field will be determined with the aid of sensitivity measurements, i.e., the quantity of exposure energy per surface unit of the light-sensitive layer (if desired in a relative measure) is determined, which is required to produce, in a test strip of the layer, a density D of 0.10 in excess of the basic density of the strip (i.e., the density of the non-exposed portions of the strip).

With U.B. uses the determination of the sensitivity effect is linked to the criteria of the minimum mirror exposure (A.U.B. uses) or the minimum outgrowth exposure (U.U.B. uses), i.e., the quantities of exposure energy just producing external noble-metal layers in accordance with the definition referred to above, which images, after washing and heating at 150 C. for one hour, exhibit an electric resistance not exceeding 100 ohms per square surface or, without this thermal aftertreatment, a resistance not exceeding ohms per square surface.

Consequently, in each practical case, the active region of silver salt concentrations according to the invention can be assessed by a standard experiment. The process is then as follows:

A series of test strips is manufactured on the basis of the light-sensitive material concerned with, with the aid of a series of sensitometer exposures, for example with the aid of a densitometric wedge.

Then each time one specimen of the strips is treated in one of a series of germ introduction baths, all of which have the same concentration of dissolved mercurous salts, the concentration of the dissolved silver salt being, however, varied, for example, by a factor 10 or With this series of germ introduction baths one is used, which does not contain silver salt, to serve as a blank test strip. Finally, the whole series is developed purely physically at the same constant temperature and for the same time in one or more stabilized or non-stabilized developers of the same composition. For each strip is then determined the LB. sensitivity, or, if the conditions chosen are suitable for the formation of an external noble-metal image, the U.B. sensitivity concerned. If desired, the standard test may be repeated for a more accurate determination of the limits of activity with the aid of a sequence of germ introduction baths, of which the concentration is varied by a lower factor. The results of this standard test may be illustrated by plotting graphically on the ordinate the negative logarithms of the quantities of exposure energy corresponding to the LB. or the U.B., sensitivity concerned and on the abscissa the logarithms of the silver salt concentrations, after which two further horizontal straight lines are drawn on the level of the negative logarithms of the exposure energies corresponding to the LB. or the UB. sensitivity concerned of the lank test strip. Then two regions of active concentrations of the silver salt confined by a diving-bell-shaped curve, the silver salt curve and a horizontal straight line, are obtained with the associated gains .in sensitivity, one for TB. and one for A.U.B. or U.U.B. sensitivities.

The same result may be obtained in a simpler man ner by counting for each test strip, in one case, the steps which exhibit a visually distinguishable difference in density with respect to, for example, the basic density of the strip, or, in the other case, the steps which exhibit, after being subjected or not to a thermal after-treatment in the manner described, an electric resistance not exceeding 100 or 18 ohms per square surface respectively, whilst these two numbers of steps are plotted on the ordinate, the logarithms of the silver salt concentrations being plotted on the abscissa. The coiresponding numbers of steps of the blank test strip are indicated in the figure in the form of horizontal straight lines. Also in this way the limitation of the regions of the active silver salt concentrations are found. When a strip is manufactored in the aforesaid manner, there are three possibilities for the final results.

( l) The strip has only an internal image throughout the density region.

(2) Up to a given density value the strip has only an internal image, but in excess of this density value an external image is formed, in addition.

(3) At all density values in excess of the basic density of the strip exhibits an external noble-metal image, which is usually superimposed on an internal image.

A method in which test strips of the type (1) are obtained is extremely suitable for the manufacture of internal photographic images and the standard test described indicates the compositions of the germ introduction baths with the increased sensitivities. A method yielding the results in accordance with (3) is particularly suitable for the manufacture of external electrically conductive images. In this case the standard test indicates the compositions of germ introduction baths with an increased U.B. sensitivity. The latter applies, in particular, to a U.U.B. If the conditions are favourable to the formation of an external image, strips according to (2) are obtained, however, for which case both for the internal image and for the external image the silver salt curves can be drawn, so that it is easy to read the advantageous compositions of the germ intro duction baths. The usefulness of a given germ introduction bath for a given use can be read Without difficulty from the test strip concerned; :it is essential for the U.B.- use of course that one or more steps of the strip should exhibit an external image, for the I.B.-use it is essential that no external image should occur in the density region to be circumscribed for this use.

In fact, there is a silver salt curve for each active concentration of the mercurous salt in the germ introduction bath. In what way a suitable, general impression of the sensitivity variation of the material concerned as a function of the concentration of the mercurous salt and of that of the silver salt in the germ introduction bath can be obtained from such a sequence of silver salt curves is shown in FIG. 1, which applies to an internal image. Although it is, in general, advisable to establish a sequence of silver salt curves in the manner described for a given light-sensitive layer, a rough assessment of the composition of the germ introduction bath which provides approximately the maximum light sensitivity for the lightsensitive layer chosen may be obtained sooner in the following manner, if uses in the field of internal images are aimed at:

By using germ introduction baths containing, as the sole metal compound, dissolved mercurous salt, a sequence or sensitometer exposures is employed to determine, by varying the concentration of the mercurous salt in the germ introduction bath the concentration w ch provides the maximum light-sensitivity. Then, on the basis of the most active germ introduction bath found, with the aid of a new sequence of sensitometer exposures, by varying the concentration of the silver salt in this special germ introduction bath, the most active silver concentration is determined. Both below and above this most active silver salt concentration there is a region of useful concentrations, confined by an activating concentration and a deactivating concentration, in which region the use of the method according to the invention produces a gain in sensitivity.

According to a preferred embodiment of the method according to the invention the germ introduction bath and the stabilized or non-stabilized purely physical developer are combined into a single bath (so-called disproportioning developer), so that the number of processes to manufacture the final internal and/or external noble-metal image is reduced by one and the method is simplified. The disproportioning developer concerned contains, consequently, on the one hand, one or more mercurous salts ais 0,05

. 7 and one or more silver salts and, on the other hand, a reducing agent for silver salts and, moreover, a stabilizing acid for purely physical developers, preferably an organic buffer acid such as citric acid and, if necessary, for stabilization, one or more ionogenic surface-active compounds, in conjunction or not in conjunction with a non-ionogenic surface-active compound. In this case, it is true, it should be prevented that images consisting of mercury, for the major part, are formed, since such mercury images, apart from the poisonousness of mercury vapour, are insufficiently preservable in view of the volatibility of mercury, so that they cannot be satisfactorily reproduced. It is therefore advisable to choose the total concentration of the mercurous salts in the disproportioning developer to be not more than mmol/ litre, whilst the total concentration of the silver salts in the said bath must then be at least twice the total concentration of the mercurous salts therein. With the manufacture of external images use is preferably made of mercurous salt concentrations of 0.5 to 10 'mmol/h'tre. When using colouring physical development, in which the metal image is afterwards removed, the aforesaid considerations do not apply, of

course.

It has furthermore been found that the measure according to the invention, if combined with the aforesaid, known measure, in which prior to the purely physical development, a compound is provided in the layer with an anion capable of reducing the concentration of free mercurous ions and not forming a subsisting precipitate with the mercurous ions under the prevailing conditions, can produce a combination effect. The said compound may be provided in the layer prior to exposure, but it may be added, as an alternative, to the germ introduction bath, in which case it is advisable to choose the total concentration of the mercurous salts in this bath to be not lower than 0.1 mmol/litre. An addition to the layer and and to the germ introduction-bath is, as a rule, not efficacious, since this does not yield an additional effect. It is obvious that the dosage of the said compound is not arbitrary, since it acts upon the limitations of the effect of the silver salt addition to the germ introduction bath and the height of the peak of the silver salt curve concerned. Initially the sensitivity is acted upon in the desired sense, but with an excessive dosage even a reduction of the maximum sensitivity may occur. Provisions should therefore be taken that the dosage should not be such that :the sometimes fairly strong positive combination effect is converted into a negative efiect, i.e., a loss in sensitivity.

For a rough determination of the compositions yielding approximately maximum gains in sensitivity, particularly if I.B. uses are concerned, the most rapid process is as follows:

1) By germ introduction baths containing, as a sole metal' compound, dissolved mercurous salt, it is first determined, with the aid of a sequence of sensitometer exposures, by variation of the concentration of the mercurous salt in the germ introduction bath, which concentration yields the maximum light-sensitivity.

(2) Then, on the basis of the germ introduction bath which has been found to be the most active in accordance with (1) with the aid of a new sequence of sensitometer exposures and by varying the concentration of the compound with the aforesaid anion in thelight-sensitive layer bath, the most active silver salt concentration is determined.

advisable to add to the germ introduction bath in which the total concentration of the mercurous salts is at least 0.1 mmol/ litre, one or more organic hydroxy acids, chosen from the group of citric acid, tartaric acid, glycolic acid, malic acid and glycerol acid. Such a quantity thereof is to be added that the deposit initially formed with the mercurous salt is again dissolved. External noble-metal images obtained with the aid of such germ introduction baths have a beautiful gloss and are excellently reproducible.

The germ introduction baths contain always a quantity of strong acid which serves to dissolve completely the whole quantity of mercurous salt. As is known, mercurous salts tend to hydrolyze. It has been found that the gain in sensitivity attainable at a maximum in accordance with the invention decreases with an increasing concentration of the strong acid in the germ introduction bath. On the contrary, however, the density homo geneity of the developed images deteriorates below a given acid concentration. In View of these two conditions, it is advisable to adjust the concentration of the free, strong acid in the germ introduction bath to a normality lying between 5X 10- and 2.l0

As stated above, the use of the method according to the invention yields, apart from a gain in sensitivity which is important for all uses, a possibility of gradation control; The last-mentioned effect is particularly important for I.B.-uses. FIG. 2 illustrates this. With I.B.-uses the density homogeneity and the depth of the density of the images obtained are, moreover, often materially improved. With U.B.-uses themethod according to the invention yields not only an increase in sensitivity but also an improvement in the adhesion of the external noble-metal images to the support, which is frequently desired with certain A.U.B. uses.

An important field of use for the method according to the invention is that of the manufacture of photographic, external, electrically conductive noble-metal layers. The term noble-metal layers is to be understood to mean herein not only layers having an uninterrupted surface but also those having patterns of which the portions are coherent or not coherent, for example, station-name dials for radio apparatus, ornamental objects, printed wirings, printed circuits, flat electric component parts, and so forth. As a rule, such a layer will be or must be subjected, subsequent to its formation, in order to modify the physical or chemical properties of the layer or of its surface, to .a physical and/or chemical after-treatment,

in accordance with the use to be made of the layer.

The external noble-metal layers obtained by purely physical development often have electric resistance values exceeding many times (to 10 times) the value calculated from the resistivity of the metal concerned. By a thermal or chemical after-treatment or by mechanical polishing this high resistance value may be materially reduced, which is important for various electrical uses.

The thermal after-treatment is carried out by heating the noble-metal layer to a temperature of at least C.

'The desired effect is attained sooner according as the temperature of the after-treatment is higher. The chemical aftentreatment to reduce the electric resistance of silver layers consists in that these layers are brought into contact with an aqueous solution contining one or more compounds separating off, therein, a potential-anion determining with respect to the silver metal, for example Cir, Br, I, CNS: CN", S 80 S 0 or OH: or a hydrogen ion. Moreover, a mechanical polishing treatment can provide the said reduction of the resistance.

For a large number of uses in the electrical, electrotechnical and decoration fields it is necessary or desirable to subject the external noble-metal layer manufactured by the method according to the invention to an electrochemical after-treatment, necessary followed by a superficial chemical conversion or coloration. To this end may be used, for example: electrolytical polishing, electrolytical deposition of metals, whilst using or not using an external current source, electrolytical coloration of the deposited metal or electrophoretical coating with a protective or insulating, or photoand/or semiconductive surface layer. Moreover, a combination of different electro-chemical and/ or chemical after-treatments may be employed. For various uses a choice may be made from a great number of mechanical after-treatments, which may be combined with the aforesaid aftertreatments. A few important suitable after-treatments of the said kind are, inter alia polishing of the surface, application of a lacquer or varnish layer to the layer surface, embedding of the layer together with the support in an insulating envelope of thermo-nardening or thermoplastic material, transfer of the layer, if desired together with the support, to a further support of high electrical qualities, also of thermo-hardening or thermo-plastic material, application of electrical connections by soldering (for example, dip soldering).

In electronics use may be made, for example, of external metal layers manufactured by the method according to the invention, in conjunction with one or more of the aforesaid after-treatments, for the manufacture of printed wirings, circuits, screening grids, switches and other component parts.

Suitable materials to be used as supports in carrying out the present method for the manufacture of internal or external photographic images are, in general, all filmforming high-polymer products which, if not yet so, are rendered superficially accessible to the various baths, for example, regenerated cellulose, wholly or partly saponified cellulose esters, paper, cotton, polyvinyl alcohol and the like.

The invention will now be described more fully with reference to a few examples.

Examples 1. A surface of about 7 of a cellulose acetate foil with a thickness of 120 and an acetyl content of 38.2% was hydrophilized by saponification. This layer was sensitized b-y impregnation, for two minutes, in an aqueous solution containing (A) 1.5 l mol of o-methoxybenzene-diazosulphonic acid sodium per litre.

Such a saponified foil was sensitized in a similar manner with the aid of a solution (B) containing, in addition: 10- mol of cadmium lactate per litre.

Of strips of these materials the silver salt curves referred to above were determined with the aid of a sequence of sensitometer exposures, whilst using the following four series of germ introduction baths:

X1O mol of mercurous nitrate and 5 l0 mol of nitric acid per litre,

5X10" mol of mercurous nitrate and mol of nitric acid per litre,

5X10 mol of mercurous nitrate and 5 10 mol of nitric acid per litre,

5X1\, 5 mole of mercurous nitrate and 10- mol of nitric acid per litre.

In each series silver nitrate concentrations increasing from zero were used.

A period of sec. elapsed between the exposure and the germ introduction with each strip; the duration of the latter treatment amounted always to 2 sec. Then the strip was washed for 5 sec. in distilled water, then developed for 7 min. in a purely physical developer containing 0.5% by weight of metol, 2% by weight of citric acid and 0.2% by weight of silver nitrate in water and finally washed in tap water. The measurement of the developed strips was carried out with the aid of a densitometer.

Finally, the LB. sensitivity was graphically determined for each strip. For the material A the results of these measurements are illustrated in the form of the four sensitivity curves in FIG. 1 (LB. sensitivity plotted against the silver salt concentration on a logarithmic scale). If desired the group of silver-salt curves may provide graphically, in a simple manner shown in the figure, a survey of the total of sensitivity variations of the material concerned as a function of the mercurous saltand of the silver-salt concentrations in the germ introduction bath. This results in three point-assemblies, which may be connected per assembly by a flowing curve.

(1) Curve a reproducing the sensitivity of the material as a function of the concentration of the mercurous salt in the germ introducing bath, if the silver salt is omitted; consequently, this curve indicates the assembly of I.B.-sensitivities aavilable for the light-sensitive material prior to carrying out the invention.

(2) Curve b reproducting also the LB. sensitivity of the material as a function of the concentration of the mercurous salt in the germ introduction bath for those baths containing, each time, such a large quantity of silver salt as corresponds to the peaks of the silver salt curves concerned; herein are indicated the assemblies of sensitivities available in the most favourable cases for the material concerned owing to the invention.

(3) Curve c in which the silver concentrations corresponding to the points of curve ([7) are plotted against the mercurous salt concentrations.

The vertical distance between the curves b and a provides directly the optimum LB. sensitivity increase which can be attained for the material A by the addition of silver nitrate to the germ introduction bath. This distance varies in this example with the concentration of the mercurous nitrate in the bath. If the sensitivity with the corresponding germ introduction bath with at silver nitrate (curve a is taken as a reference point (i.e., if this sensitivity is assumed to be equal to l), the relative LB. sensitivity with the bath of optimum activity, containing a quantity of mercurous nitrate corresponding to a concentration of:

5 10 mol/litre:3.5

Concentration of the mercurous nitrate in the germ Relative LB.-

introduction bath sensitivity 5X10- mol/litre 19.1

5X10- mol/litre 36. 3

FIG. 1 shows furthermore the curve 12 for the material B From the test material it may be concluded that the anti-regression effect of the cadmium lactate in the layer and of the silver nitrate in the germ introduction bath are additive, so that in the method according to the invention the presence of the anti-regression agent in the light-sensitive layer can be utilized to full advantage.

The I.B.-sensitivity increase attainable owing to the presence of the cadmium lactate in the light-sensitive layer amounts, in the present example, if the sensitivity values of the curve b are taken as reference points (:1), for a germ introduction bath containing a quantity of mercurous nitrate corresponding to a concentration of 5 l0- mol/litre, to a factor of 13.8, for a bath with a concentration of 5 X 10- mol/ litre, to a factor of 4.7 and for a bath with a concentration of 5 X 10* mol/litre, to a factor of 1.7.

In this example and in the following examples colouring physical development may be carried out, for example, in blue-green with the aid of a developer containing 0.08% of dimethyl-amino-4-phenylamine-nitrate, 5% of tartaric acid and 0.4% of silver nitrate in water, to which is added, per 25 cm. 2 cm. of a 10% solution of a-naphthol in ethanol. The silver image may be removed by means of a liquid containing potassium ferric cyanide and sodium thiosulphate. Since the effect of the addition of a silver salt to a germ introduction bath is apparently based on the action upon the metal germ formation and the purely physical development is only the method visualizing the effect already available in a latent state, it is not a surprise'that this effect is also obtained, when the aforesaid colouring development or any other purely physical development whatever is employed.

II. A cellulose tri-acetate foil saponified to a depth of 6a was sensitized by means of the solution B of Example I. In the manner described in Example I the silver salt curve was determined for strips of'this material, in this AgNOa, mols/litre relative A.U.B.- sensitivity 1 1X10- 2 3X10 1. 5 5X10- 0. 7

In those cases in which the germ introduction baths contain 1 10 or 3.10 mol of AgNO per litre, the minimum mirror exposure was reduced by a reasonable factor.

111. 'A cellulose tri-acetate foil saporn'fied to a depth of 6,41. was sensitized with the aid of the solution B of Example I. In the manner described in the preceding examples the silver salt curve was determined for strips of the said material, in this case, however, with respect to the outgrown, external image. Use was made of germ introduction baths containing, per litre, 5 X10 mol of mercurous nitrate, 10 mol of nitric acid and silver nitrate in concentrations as per following table. The strips were developed in a stabilized, physical developer obtained by dissolving Metol (0.025 mol/litre) Citric acid (0.1 mol/ litre) 'Silver nitrate (0.01 mol/litre) Lissapol N (0.02% by weight), and Armac 12 D. (0.02% by weight),

7 in distilled water. Lissapol N is a condensation product AgNO moIs/litre Developing time in min.

0 10" 3X10- 10- 3X10- 10 3X10 From this table it is evident to what extent the'exposure required to obtain U.U.B., when using one of these developing times, can be reduced by adding the indicated concentration of the silver nitrate to the germ introduction bath.

With respect to the germ introduction baths not containing silver nitrate it should furthermore be noted that, with a developing time of 30 min, the exposure required to obtain U.U.B. appeared to be 8 times the minimum outgrowth exposure (with a developing time of 180 min). With a developing time of 60 min. an exposure twice the minimum outgrowth exposure could yield U.U.B. and with a developing time of min, the minimum outgrowth exposure could suflice.

IV. A superficial layer of 6.7 1. of the cellulose acetate foil of 120p. in thickness, having an acetyl content of 42% was hydrophilized. This layer was sensitized by impregnation of the foil for 2 min. in a solution B of Example I.

In the manner described in Example I the silver salt curves of strips of this material were determined with the aid of sensitiometer exposures, whilst using the same series of germ introduction baths.

Hereinafter are indicated the results for the relative LB. sensitivities with the germ introduction baths containing such a large quantity of silver nitrate as corresponds to the maxima of the silver salt curves concerned. The reference points are again as in the following examples (unless indicated otherwise) the LB. sensitivities with the corresponding germ introduction baths from which the silver nitrate is omitted.

It should be furthermore noted that the image quality (homogeneity and the uniformity of the image density) was always found best with baths of optimum activity. Attention is finally drawn to the more or less parallel course of the sensitivity elfect and the gradationeifect with reference to the example of the germ introduction bath containing 5 10 mol of mercurous nitrate per litre (see FIG. 2).

V. Filter paper was sensitized by impregnation, for 2 min, in a solution B of Example I.

With this paper tests were made also in the manner described in the preceding examples to assess the effect of the addition of silver nitrate to germ introduction baths containing mercurous nitrate. It will suflice to state the relative I.B. sensitivities associated with the maxima of these silver salt curves.

[AgNOa] [HNO Relative [Hgg(NO3)2] mols/htre mols/litre mols/litre LB.

sensitivity 5X10- 5X10 l. 7 varying from 10- 2.0 ca. 10'? to 10' 2. 3 ea. 10*. 10- 3. 6 10*" Tests carried out in the manner described in the preceding examples, use being made, however, of a light-sensitive material obtained by sensitizing unilaterally white, wood-free litho paper (70 g./m. yielded similar results. VI. A layer of regenerated cellulose of 40a in thickness was sensitized with the aid of solution B of Example I, after which it is wiped off and dried. Strips of this foil, exposed to a sensitometer, were immerged, each, for 2 sec. in the germ introduction baths containing, all of them, 5 10- mol of mercurous nitrate and 10 of nitric acid per litre, differing, however, from each other, by the silver nitrate content as indicated in the following table.

Relative LB sensitivity AgNO;, mols/litre Instead of choosing mercurous and silver nitrate and nitric acid in the germ introduction bath, other anions, for example, the perchlorate ion in the bath may yield completely similar results.

V11. A cellulose acetobutyrate foil was sapom'fied superficially to a depth of about 6 impregnated for two minutes in a. solution containing, per litre of water, 2X mol of p-methoxy-benzene-diazosulphonic acid sodium and 10 mol of cadmium lactate, after which it is wiped OE and dried in air in darkness.

In order to determine the LB. sensitivity sensitometer exposures were carried out, use being made of a highpressure mercury-vapour discharge lamp of 250 w. in a quartz bulb. For the 'y determination the exposure was carried out at a distance of about 8 cms. behind a densitometric wedge (D=0.l5) for /s to A2 sec.

About sec. after the exposure, the exposed strips were dipped for 2 sec. in germ introduction baths containing 5 10- mol of mercurous nitrate, 4X10" mol of nitric acid per litre and a varying concentration of silver nitrate, as is indicated in the joined table. After washing in distilled water purely physical development was carried out with the developer of Example I, at a temperature of about C. for 10 min. for the sensitivity tests and for 7 min. for the gradation tests. The results of the tests are indicated in the following table:

termine the gradation Were carried out. The results of the two determinations are given in the following table.

AgNOa HNOQ Relative HgflNOah mols/ mols/ 6.35 log I.B. Gamma 2 mols/litre litre litre E 1 sensitivity 1. 5X1O- 0 1. 5X10 0.00 1 1. 1 10- 1. 5X10- 0. 27 l. 9 1. 2X10 1. 5X10 0. 48 3. O 1. 4X10- 1. 5X10 0. 65 4. 5 Not de- 1. 1 10- 1. 5 10- 0. 68 4. 8 ter- 1. 2X10- 1. 5X10 0.48 3. 0 mined 1. 4X10- 1. 5X10 0.27 1. 9

0 5X10- 0. 00 1 Very low 2X10- SXIO- 0.71 5. 1 2. 0.

2 )(10- 5 X10 0. 84 6. 9 not determined 0 5 10- 0. 00 1 Very low. 4 10- 5X10- 0. 65 4. 5 Do.

lXlO- 5X10 1.07 11. 8 0.9.

1X10- 5X10 not de- 1. 8.

termined 1 For a density D=0.1; developing time: 10 min. 3 Developing time for the series with Hg2(N03) =5X10- m: 5 min.;

for the series with Hg2(NO =5 10- m.: 6 min. The sensitivity or" the material treated with germ introduction baths not containing silver salt is low; in this case no densities in excess of D=0.5 can be obtained. With silver salt in the germ introduction bath material gains in sensitivity are realized, whilst, if desired, densities exceeding D 3 can be attained, so that it may be said that the significance of this light-sensitive material, treated by the germ introduction method, has become evident only by using the method according to the invention.

1X. Superficially saponified cellulose acetobutyrate foil was sensit zed by impregnation for 2 min. in a 0.1 molar solution of sulphito-diathylene diamine-cobaltic chloride, Co(C lI.,N H SO Cl, and dried in air. Strips of the foil thus obtained exposed to a high-pressure mercuryvapor lamp and a sensitonieter was treated for a few seconds with the following germ introduction baths. Development took place in the purely physical developer of Example I for 10 min.

The eifect oi the addition of the silver nitrate to the germ introduction bath is evident from the following table.

AgNO in the germ introduction 4.23-log E Relative bath in mols/litre for D=0.1 IB.- Gamma 2 sensitivity 0. 33 2. 1 0. 20 l. 6 0. 17 1. 5 0. 04 1. 1 1 x10- 0. -l 0.4

1 E is the exposure energy in ergs/cmfl of film surface. 2 Gamma is the slope of the straight portion of the density curve.

VIII. A superficially sapom'fied layer of cellulose acetobutyrate was sensitized by impregnation, for 2 min, in a 0.4 n aqueous solution of hydroxy-l-diazo-2-rnethyl-6- benzene-sulphonic acid 4 and then dried. Strips of this light-sensitive material exposed to a high-pressure mercury-vapor lamp were treated for about 5 sec. with germ introduction baths containing or not containing silver salt, of which the composition is indicated in the table; then the strips were purely physically developed in a developer composed in accordance with the recipe of Example I. Apart from exposures with the aid of a timedial sensitometer to determine the sensitivity, also a few exposures with the aid of a densitometric wedge to de- Hg (NO AgNO -Relative NHO3 mols/litre mole/litre mols/litre LB sensitivity 5 10- 0 1 5X10- 10" 2. 6 5 1O- 10- 2. 3 5X10 4X10 1. 3

The superficially saponified foil of Example IX was impregnated for 2 min. in a 0.1 molar solution of o-nitromandelic acid nitril in 40% of alcohol and then wiped off and dried. Strips of this material were, subsequent to exposure with the aid of a sensitometer, treated with germ introduction baths having compositions as indicated in the following table. Physical development: as in Example I.

Effect of the addition of silver nitrate to the germ introduction bath:

2( O3)2, AgNO3, Relative NHO; mols/litre IIlOls/litre mole/litre I.

sensitivity 5X10- 0 1 5X10- 10- 3. 7 5X10 10- 1. 8

r e r 7 Number of Relative Hg2(N s)2, AgNOa, HNOs, steps with I.B.-sensi- Gamma mols/htre mols/litre mols/litre a (1121168151337 tivity 5X1O" X10- 4 1 5X10T 10 7. 9 1.5 10' 5X10 11 11.2 3. 6 l0- 5Xl0- 10 7. 9 6. 5 l0 5X10 4 1 about 1.8

0 5X10' l 1 10- 5Xl0- 11 31. 6 about 1.0 10 5X10' 11 31. 6 5. 5 10- 5X10 10 22. 4 7. 5 10 5X10' 7 7. 9 about 1.0

With two further light sensitive materials, obtained by impregnation for 2 min. of the aforesaid superficially saponified foil in (A) A solution of 1% of p-hydroxybenzenediazosulfonic acid-potassium in water and (B) A solution of 2% of chloro-4 diethoxy-2,5 benzenediazosulfonic acid-l in water, the elfect of the addition of silver salt to germ introduction baths was determined.

The results of two series of exposures of these materials are indicated hereinafter.

The germ introduction baths contained invariably per litre 5X l0 mol of mercurous nitrate and 5X l0 mol of nitric acid. The development was carried out as stated above in this example.

MATERIAL (A) XII. An acetyl-cellulose foil having an acetyl content of 42% was rendered superficially hydrophilic by saponification and then sensitized by impregnation in the solution B of Example I.

The. LB. sensitivities were measured at a number of exposed strips of this material, whilst using germ introduction baths containing or not containing silver nitrate, which baths had the properties of purely physical devel- 7 opers by adding metol and citric acid. The compositions of these disproportioning developers were as follows:

p Methylamino phenolsulphate (metol): 1.5 X10 mol/ liter (0.5%), Citric acid: 1O mol/ litre (2% Mercurous nitrate: 5 X 10* mol/ litre,

whilst the silver nitrate concentration was varied as indi- I cated in the following table. The strips stayed in the bath From further tests it has been found that solutions containing 10 'to about 10 mol of silver nitrate per litre have the most favorable properties, if the mercurous nitrate concentration per litre amounts to about 5X10" mol.

If strips are treated with a corresponding series of baths, from which the metol is omitted, these strips being then developed for 10 min, in the purely physical developer of Example I, a completely similar variation of the relative LB. sensitivity is found. The maximum sensitivity is in this case equal to that when disproportioning developers are used, but the use of these baths simplifies, as a matter of course, the process.

Other satisfactory disproportioning developers are:

(a) Amino-4-phenylamine nitrate: 4.7x 10* mol/ litre,

Tartaric acid: 3.3x l0- mol/ litre, Mercurous nitrate: 5 10 mol/ litre, and Silver nitrate: from 10* to 10- mol/litre.

By adding, for example, 2. cm. of a 10% solution of oznaphthol to 25 cms. of the said solution the bath may obtain, moreover, the properties of a colouring physical developer.

(b) Hydroquinone: 1.4X10- mol/litre,

Acetic acid: 2.5 mol/litre, Mercurous nitrate: 5 X 10- mol/ litre, Silver nitrate: from 10 to 10 mol/litre solution.

The best results are obtained in the latter case, when the bath contains about l0 mol/litre of silver nitrate.

XIII. A strip of'the foil sensitized as described in Example H was subjected to an exposure of about twice the minimum mirror exposure, behind a line negative, with the aid of a 125 w. high-pressure mercury-vapour lamp at a distance of 60 cms. and then introduced into a disproportioning developer of the composition:

Metol: 1.5 X 10 mol/litre,

Citric acid: 101 mol/ litre, Mercurous nitrate: 10- mol/ litre, Silver nitrate: 10 mol/ litre.

j 15 0 C. Corresponding results were obtained with other disproportioning developers, for example, those described 'in' the preceding example.

XIV. The quantities of exposure energy required to obtain a density of D=1.00 in excess of the basic density of four light-sensitive materials obtained by sensitizing cellulose tri-acetate foil superficially saponified to a depth of 6 with aqueous solutions containing: 7 10- mol of p-methoxy-benzene-diazosulphonic acid-sodium and 7 1() mol of resorcinol per litre and having dissolved in it, in addition, sodium lactate as indicated in the following table, were compared (use was always made of a solution of lactic acid neutralized to pH=5 with sodium hydroxide).

The latent metal images were formed, after the exposure of strips of these materials, with the aid of a sensitometer, by using aqueous germ introduction baths containing 5 10- mol of mercurous nitrate and 10- mol of nitric acid per litre, to which quantities of silver nitrate were added, corresponding to the maxima of the silver salt curves; for comparison the bath without silver nitrate was included in the experiment. For 7 the germ images were developed in the purely physical developer of Example 1. The results of the determination of the sensitivity are indicated in the following table.

RELATIVE REGIPROCAL QUANTITY OF EXPOSURE EN- ERGY REQUIRED TO OBTAIN A DENSITY OF D=L IN EXCESS OF THE BASIC DENSITY OF THE LAYER In the last column, between brackets, are indicated the numerical values obtainable by addition of the two effects.

XV. The superficially saponified cellulose triacetate foil referred to in Example XIV was sensitized by impregnation in an aqueous solution containing 7 10- mol of p-methoxy-benzene-diazosulphonic acid-sodium and 7 lO mol of cadmium lactate per litre.

After the sensitometer exposure of the layer the germ formation took place in aqueous solutions with or without silver salt, containing 10- mol of mercurous nitrate and 10 mol of nitric acid per litre, and in which, moreover, sodium lactate had been dissolved, prepared as described in Example XIV, in concentrations indicated in the following table.

After physical development for 7 min. in a developer according to the recipe of Example I, measurements were carried out on the developed strips, the sensitivity being related, as in the preceding example, to a density of D=l.00 in excess of the basic density of the layer. Results:

Germ introduction baths with Na-lactate, mols/litre As sensitivity reference point (sensitivity=1) is chosen the sensitivity of a strip treated with the corresponding germ introduction bath not containing either silver nitrate or sodium lactate.

XVI. Sensitized foil of Example 11 was exposed, after drying, behind a line negative with a quantity of energy equal to the minimum mirror exposure. Then it was treated with an aqueous solution containing 5X 10 mol of mercurous nitrate, 10- mol of silver nitrate and 10 mol of citric acid per litre and then developed as described in Example I. The resistance of the resultant grown external image was 2.7 l0 ohms per square sufrace, which value dropped to 3.2 ohms per square surface after a thermal after-treatment for one hour at 150 C.

When the bath used prior to the physical development contained instead of citric acid, l0 mol of nitric acid, an image with a resistance of 2X10 ohms per square surface was obtained only with double the said exposure energy, which corresponded to the minimum mirror exposure, which value dropped, after the same thermal after-treatment, to 12 ohms per square surface.

XVII. Strips of sensitized foil as in Example II were exposed, behind a line negative, to a high-pressure mercury-vapour lamp in a series of mirror exposures. Subsequent to exposure the strips were treated with a solution of (a) 5 10 mol of mercurous nitrate, 10" mol of silver nitrate and 10* mol of nitric acid per litre, or with a solution of: (b) 1.5 10 mol of mercurous nitrate, 10 mol of silver nitrate and 10- mol of nitric acid per litre, after which the material was developed purely physically in the developer of Example I. The resistances (in ohms per square surface) of the resultant grown, external metal images and of those attained subsequently by heating for one hour at 150 C. in a drying cabinet are indicated in the following table. The exposure energies are indicated with respect to the minimum mirror exposure as a unit: the relative mirror exposure energy.

After exposure treated After exposure treated with solution a with solution b Relative mirror exposure energy Measured Measured Direct measafter heat- Direct after heaturement ing at 150 measureing at 150 C. for one ment C. for one hour hour 2X10 7 1. 3X10 8 5. 4x10 3. 8 2. 6X10 2. 7 1. 3x10 2.1 3. 4x10 2.3 1.8)(10 1.8 6.1)(10 1. 2 6X10 0.33 5. 5 X10 1. 2 4. 3X10 0. 23 3. 5X10 0. 8 3.1 10 0.18 3. 6X10 0.8 3. 4X10 0 16 3. 5X10 0 14 3. 4X10 0 14 When the images, marked (1) and (2) and (3) in the table, are polished by rubbing thoroughly with a soft plug of cotton wool, the resistance drops to 75, 14 and 6 ohms per square surface respectively.

XVIII. A film strip was sensitized as described in Example II and then exposed behind a line negative to a high-pressure mercury-vapour lamp with an exposure energy of about 10 times the minimum mirror exposure. Subsequently to this exposure, the foil was treated with an aqueous solution of 5 10 molar mercurous nitrate, 5 10 molar silver nitrate and 5x10 molar nitric acidI and then developed purely physically as in Example The resistance of the metal image thus obtained amounted to 4 10 ohms per square surface.

When this image was then subjected to an after-treatment with one of the solutions mentioned hereinafter, this resistance dropped below at least ohms, as indicated in the following table.

XIX. A foil sensitized as described in Example II was exposed in a vacuum pressure frame behind a cross grid negative with the aid of a high-pressure mercury-vapour lamp with an exposure energy of about 5 times the minimum mirror exposure. Subsequently to the exposure the foil was treated with a solution of 5X 10 mol of mercurous nitrate, 2X10 mol of silver nitrate, 5X10" mol of rliitric acid and then developed as described in Examp e Then the image was intensified electrolytically in an acidic copper-deposition bath containing 20% by weight of copper sulphate (SH O) and 6% by weight of sulphuric acid for 10 to 15 min. with a current density of 200 to 500 ma./dm. of grid surface. The width of the E9 grid lines thus obtainable amounted to l0/,u, whereas the distance between the lines was '25-30/,LL.

' What isrclaimed is:

l. A method of producing noble-metal images on nonmetallic supports whiohmethod comprises sensitizing a non-metallic support by treating said support with a lightsensitive compound selected from the group consisting of hydroxy-benzene diazonium compounds, hydroXy-naphthalene diazonium compounds, aromatic diazo sulfonates, sulfito-diethylene-diamine cobaltic chloride and o-nitromandelic acid nitrile, exposing said sensitized support to light, treating said exposed support with an aqueous nu cleus introduction solution containing a mercurous salt in a concentration of more than 1 ,umol/liter and a silver salt in a concentration of at least twice that of the mercurous salt to thereby produce a latent metallic image on said support and then developing said latent metallic image by applying to said latent metallic image an aqueous solution of a reducible compound of a metal selected from the group consisting of gold, silver, platinum and mercury and an organic reducing agent capable of reducing said reducible compound to metal. a

2. The method of claim 1 wherein the light-sensitive compound is an aromatic diazo sulfonate.

' 3. The method of claim 1 wherein the sensitized sup port contains at least one anti-regression agent.

4. The method of claim 1 wherein the nucleus intro duction solution and the physical developer are a single solution and contain mercurous salts in the concentration of 0.1 to mmol/litre, silver ions in a concentration at least twice that of the mercurous ions, a reducing agent for said silver ions, and an organic buiIer acid.

5. The method of claim 1 wherein the intensity of exposure is suflicient at least so that upon completion of the physicaldevelopment step the resultant noble metal image has a resistance not exceeding 10 ohms per square surface. I e I 6. The method' of claim 5 wherein the aqueous nucleus introduction solution contains dissolved mercurous salts in the concentration of at least 0.1 mol per litre and an organic hydroxy acid selected fiom the group consisting of citric acid, tartaric acid, glycolic acid, malic acid and glyceric acid, said hydroxy acid being employed in a quantity suflicient to dissolve any precipitate initially formed.

7. The method of claim 1 wherein the mercurous salt is introduced into the nucleus introduction solution in a diluted strong acid and the normality of the nucleus introduction solution is between 5 10 and 2X10? 8. The method of claim 1 wherein a physical developer forms an organic dye image simultaneously in place with the noble metal image.

References Cited in the file of this patent I UNITED STATES PATENTS OTHER REFERENCES Alink et al.: Journal of the SMPTE, vol. 54, March 1950, pages 345-350. Copy in Scientific Library. 

1. A METHOD OF PRODUCING NOBLE-METAL IMAGES ON NONMETALLIC SUPPORTS WHICH METHOD COMPRISES SENSITIZING A NON-METALLIC SUPPORT BY TREATING SAID SUPPORT WITH A LIGHTSENSITIVE COMPOUND SELECTED FROM THE GROUP CONSISTING OF HYDROXY-BENZENE DIAZONIUM COMPOUNDS, HYDROXY-NAPHTHALENE DIAZONIUM COMPOUNDS, AROMATIC DIAZO SULFONATES, SULFITO-DIETHYLENE-DIAMINE COBALTIC CHLORIDE AND O-NITROMANDELIC ACID NITRILE, EXPOSING SAID SENSITIZED SUPPORT TO LIGHT, TREATING SAID EXPOSED SUPPORT WITH AN AQUEOUS NUCLEUS INTRODUCTION SOLUTION CONTAINING A MERCUROUS SALT IN A CONCENTRATION OF MORE THAN 1 UMOL/LITER AND A SILVER SALT IN A CONCENTRATION OF AT LEAST TWICE OF THE MERCUROUS SALT TO THEREBY PRODUCE A LATENT METALLIC IMAGE ON SAID SUPPORT AND THEN DEVELOPING SAID LATENT METALLIC IMAGE BY APPLYING TO SAID LATENT METALLIC IMAGE AN AQUEOUS SOLUTION OF A REDUCIBLE COMPOUND OF A METAL SELECTED FROM THE GROUP CONSISTING OF GOLD, SILVER, PLATINUM AND MERCURY AND AN ORGANIC REDUCING AGENT CAPABLE OF REDUCING SAID REDUCIBLE COMPOUND TO METAL. 